Researchers asked over 1000 fertile and infertile couples about the dietary habits and drug use, and found several strong associations - fertile men and women reported eating more vegetables, fruit, legumes and eggs than those who were classified as infertile. Fertile men and women were also much less likely to be smokers, they drank less alcohol and were less likely to have ever taken illicit drugs.

'While we know that infertility is a multifactorial disease, the infertile individuals in our study clearly had worse recreational and nutritional habits than the fertile,' said Professor Andrea Salonia, director of the Urological Research Institute at the Ospedale San Raffaele in Milan, Italy.

Professor Salonia pointed out that many of the nutrients in these foods, including zinc, selenium and antioxidants, have been shown in other studies to improve both male and female fertility.

'A balanced and healthy diet would not only provide a benefit in terms of general health but also in male and female reproductive health,' he added.

Also speaking at the conference was Dr Niels Jørgensen, a consultant at Rigshospitalet in Copenhagen, Denmark, who reported on the decline in male sperm quality seen in various countries across Europe since 2000.

It had been previously been reported that male sperm had decreased in number as well as quality by 50 percent over the last 50 years of the 20th century, but it was not clear whether this was because of the limitations of historic data. Dr Jørgensen looked at several more recent studies conducted in Finland, Spain, Sweden, Denmark and France. While some showed falls of 15 to 20 percent in the number and quality of sperm in the first decade of this millennium, others showed no change or even a slight improvement.

However, Dr Jørgensen highlighted that only 25 percent of young men have optimal semen quality. Meanwhile, a further 20 to 30 percent have reduced numbers and quality of sperm and it is likely that it will take them longer for them to become fathers. Ten to 15 percent of young men have sperm counts so low that they are likely to need fertility treatment if they wish to become fathers.

Dr Jørgensen told the meeting in Lisbon that he believes that modern chemicals are to blame for this decline is sperm numbers and quality. 'Humans are globally exposed to many classes of chemicals with endocrine-disrupting potential. Exposure during fetal life may compromise testicular development, leading to reduced semen quality in adulthood,' he said. Such chemicals are found in sunscreen, cosmetics, frying pans, cars, foods and some items of clothing, he added.

Researchers from Spain also reported to the Lisbon meeting their finding that women over the age of 44 have only a 1.3 percent chance of having a baby through IVF using their own eggs.

Dr Marta Devesa from the Hospital Universitari Quirón-Dexeus in Barcelona, Spain, described the results of her 12-year study involving 4000 women at the hospital. While women aged 38 or 39 had a 24 percent chance of success with IVF using their own eggs, this declined to 15.6 percent among 40 and 41-year-olds, and 6.6 percent among those aged 42 and 43.

'Women of 44 or older should be fully informed about their real chances of a live birth and counselled in favour of egg donation,' she said at the meeting, as reported in the Guardian.

To improve chances of conception, men should drink a pint of beer daily, cut down on coffee, eat more fruit and vegetables (beware a coating of sperm-harming pesticides), and avoid vegetarian or vegan diets...